Golf cart BMS problems....

[Twrecks]

I have recently purchased 3 power queen batteries to do a budget build on an EZGO golf cart. Ran the cart about 15 miles which i found impressive considering the previous Lead acids barely made 5 miles. Went to charge the packs since i was reading about 30% power left, and hooked them all in parallel to a victron blue IP-65 15Amp charger. It went through the full charge cycle and showed that the batteries where all fully charged, but when i try to run the cart again the first battery in series instantly opens the circuit as if it was under volting. Im almost to the point of ripping all 3 batteries open and just making a single 36 volt system. Is there any ideas on how i could further test the current batteries, and if not any suggestions on what BMS to use for a 36 volt system.

The cart is a 1995 that i rebuild pretty much from ground up, with whole frame being rusted out. Hence the budget route

 

[time2roll]

As if it was under volting? How about putting a meter on it and posting the actual voltage both resting and in service. Check the entire pack too.
For testing I would charge them again separately and monitor the voltage on the battery terminals.

 

[stok]

can the batteries be series connected? you need to find out if the FETS in the bms is rated to at least 45v to allow the voltage of 3 connected in series (43.2v fully charged) to pass through without damaging the FETS.

the reason the fets didnt blow the first time might be that the batteries voltage was bellow that of the fets, eg. each battery was 13.3v (39.9v total) and after charging fully it pushed the voltage above the threshold of the FETS

 

[Twrecks]

Ok so i did some more testing and heres what i found. For one my multimeter sucked. I got a new more precise klein MM and the batteries in Series read 40.42 V. Yes per the manufacture they can be hooked in series, not sure about charging them in that manner though as i have been charging them in parallel.

What i believe to be the problem is one of the batteries BMS is shot. When i hook a 12 volt LED lamp up that pulls no more than 2.5 Amps, 2 of the batteries will power the lamp no problem. The 3rd will immediately shut down the load. My thoughts are that if it is shutting down on such a small load it is probably doing the same on the cart. Plan to change the BMS in the single cell. If this proves to be correct and is fairly easy then i will definitely be tearing into other 3 cells to make one system with a singular 12S 200A BMS

 

[gormant737]

I am trying to DIY a new 36v battery system for a 1992 EZGO. I would be curious if you have any updates. FWIW, I conversed with a guy on YouTube who had a video on this topic. He informed me running 3 cheapo Amazon batteries in series like you did would indeed fry one of the batteries BMS. I guess he was right. I'm very novice and not inclined to order 3 new batteries only to rip them apart trying to rig something. Thanks for any insights!